Wall-arranged giant ring-shaped straight-through pulverized coal burner

ABSTRACT

A wall-arranged giant ring-shaped direct-current pulverized coal burner includes burner nozzles arranged on four side furnace walls of a boiler. The burner nozzles on the four side furnace walls form a wall-tangential combustion mode in the furnace, and the burner nozzles on each side furnace wall are arranged in a ring by a plurality of small nozzles to form a giant ring-shaped combined nozzle. There is a plurality of small nozzles arranged in a ring on each side furnace wall to form a giant ring-shaped combined nozzle. The giant ring-shaped combined nozzles on the four side furnace walls may form a wall- tangential combustion mode in the furnace. Through the mutual entrainments of the multiple airflows in the giant ring-shaped combined nozzle and the mutual support of the fireside and back-fire-side airflows, the stiffness of each airflow may be effectively enhanced.

TECHNICAL FIELD

The present disclosure relates to the technical field of boiler burners,particularly to a wall-arranged straight-through pulverized coal burner.

BACKGROUND

The existing straight-through pulverized coal burners of largepulverized coal boilers in power plants are mainly arranged in afour-comer tangential mode or a four-wall tangential mode. In thefour-comer tangential mode and the four-wall tangential mode, allstraight-through burners are simply arranged along the same verticalline at four corners or on four furnace walls. For example, Chineseinvention patent with No. CN102494333B discloses a single-fireballtangentially-firing boiler for the burning of anthracite; and Chineseutility model patent with No. CN204358718U discloses a nozzle device ofa burner of a wall-type tangential firing pulverized coal boiler.

In the existing arrangements, the stiffness of each single airflow isused to resist strong impingement of the synthetic swirling flue gasflow (or upstream gas flow) in the furnace. Furthermore, due to thenarrow gap among the vertically arranged nozzles, air supplementcondition at the back-fire side of the injected airflow is poor, whichfurther increases the deflection of the injected airflow along thehorizontal direction and even leads to the phenomenon of airflowscouring the furnace walls. Therefore, under the condition that thelinear arrangement in each burner group remains unchanged, thetraditional improvement measures include: grouping burner nozzles alongthe furnace height direction to increase the distance between burnergroups and to improve the problem of insufficient air supplement at theback-fire side of each group of burner nozzles; adopting large-chamferarrangement to improve air supplement conditions at the back-fire sideof the comer-injected airflows: adopting wall-arranged burners to enablethe burners to be far away from the downstream wall surfaces, so as tobetter improve the air supplement conditions on the back-fire side ofthe airflow. However, all the above improvement measures have limitedeffects and have failed to completely solve the problem of largedeflection of the injected airflows because the single airflow from eachburner nozzle cannot resist the strong impingement force of the swirlingflue gas and the upstream airflow. So, it is difficult to control theactual combustion tangent circle diameter in the furnace, and thephenomenon of airflow scouring on furnace walls occurs sometimes,resulting in the occurrence of major accidents such as combustioninstability, slagging, high-temperature corrosion, flue gas temperaturedeviation, and over-temperature tube explosion.

SUMMARY

A technical problem to be solved by some embodiments of the presentdisclosure is to provide a new wall-arranged giant ring-shapedstraight-through pulverized coal burner, which is used to solve theproblems of airflow deflection and the subsequent flame scouring on thefurnace walls caused by the insufficient airflow rigidity in existingboilers, as well as the problems of slagging and high-temperaturecorrosion on the heating surfaces of the furnace caused by the flamescouring on furnace walls.

In order to solve the above problems, a wall-arranged giant ring-shapedstraight-through pulverized coal burner is provided. The burner includesburner nozzles arranged on four side furnace walls of a boiler, and theburner nozzles on the four side furnace walls form a wall-tangentialcombustion mode inside the furnace. Each burner nozzle on each sidefurnace wall includes multiple small nozzles arranged along a ring toform a giant ring-shaped combined nozzle.

In some embodiments, the small nozzles forming the giant ring-shapedcombined nozzle are arranged along a circular ring, an elliptical ringor a rectangular ring.

In some embodiments, in the main combustion region inside the furnace, aplurality of the giant ring-shaped combined nozzle are installed on eachside furnace wall along a furnace height direction.

In some embodiments, on each side furnace wall corresponding to the maincombustion region inside the furnace, the giant ring-shaped combinednozzle includes a plurality of small primary air nozzles and a pluralityof small secondary air nozzles arranged along a ring.

In some embodiments, the plurality of small primary air nozzles and theplurality of small secondary air nozzles are arranged at intervals withone another along a ring.

In some embodiments, the plurality of small primary air nozzles and theplurality of small secondary air nozzles are arranged on a circularring, an elliptical ring or a rectangular ring in a two-two orthree-three concentrated mode.

In some embodiments, the plurality of small primary air nozzles and theplurality of small secondary air nozzles are arranged on two concentriccircular rings, two elliptical rings or two rectangular ringsrespectively.

In some embodiments, the plurality of small primary air nozzles and theplurality of small secondary air nozzles are respectively arranged ontwo circular rings which have equal diameters and are not concentric.

In some embodiments, on each side furnace wall corresponding to aburnout area at an upper part of the furnace, the giant ring-shapedcombined nozzle includes a plurality of small separated over fire airnozzles arranged in a ring.

In some embodiments, the small nozzles installed on each side furnacewall can be adjusted upward, downward, leftward and rightward.

Compared with the prior art, the present disclosure has the followingbeneficial effects.

In some embodiments of the present disclosure, on each side furnacewall, the plurality of small nozzles is arranged along the ring to formthe giant ring-shaped combined nozzle, and the giant ring-shapedcombined nozzles on four side furnace walls can form the wall-tangentialcombustion mode in the furnace. The giant ring-shaped combined nozzlecan effectively enhance the stiffness of each airflow through the mutualentrainment of the airflows within the giant ring-shaped combined nozzleand through the mutual support of the fireside airflows and theback-fire side airflows, thereby alleviating the phenomenon of flamescouring on the furnace walls caused by the rapid attenuation of theairflow stiffness and thus fundamentally reducing the risk of slaggingand high-temperature corrosion on the heating surface of the furnace,

Different from the one-level mode in the existing boiler in which asingle airflow from the burner nozzle directly interacts with the mainflue gas inside the furnace, some embodiments of the present disclosureadopt a two-level mode; more specially, firstly multiple single-burnernozzles are assembled into a giant ring-shaped combined nozzle, and thenthese combined airflows injected from the giant ring-shaped combinednozzle interact as a whole with the main flue gas inside the furnace. Asan intermediate level between the lower level of a single small nozzleand the higher level of the whole furnace burners, the giant ring-shapedstraight-through pulverized coal burner makes the combined airflows hasa strong overall stiffness and thus the resistance to the transverseimpingement of the swirling flue gas inside the furnace, so the schemeof burner present in this disclosure has a stronger constraint on themain swirling flue gas inside the furnace. Therefore, the combinedairflows injected from the giant ring-shaped combined nozzle have astrong anti-deflection ability, which better overcomes the huge problemthat flow aerodynamic conditions inside the furnace become more and moredifficult to be organized with the increase in boiler capacity, andthereby forming a stable and reasonable actual combustion tangentialcircle. So, the burner in the present disclosure completely overcomesthe difficult problem of poor air supplement condition on the back-fireside of the airflows caused by the vertical arrangement of burners inthe traditional burner scheme, thus effectively eliminating thephenomenon of flame scouring on furnace walls; as a result, the problemof slagging and high-temperature corrosion on the heating surface of theboiler with large capacity has been fundamentally solved. Furthermore,some embodiments of the present disclosure can also improve thecombustion uniformity in the furnace and increase the combustiontemperature, which is conducive to promoting combustion stability oflow-quality coal and reducing the generation of nitrogen oxides.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a boiler using a wall-arranged giantring-shaped straight-through pulverized coal burner according to thepresent disclosure.

FIG. 2 is a schematic diagram of the giant ring-shaped combined nozzleformed by small nozzles with square end sections.

FIG. 3 is a schematic diagram of the giant ring-shaped combined nozzleformed by small nozzles with circular end sections.

FIG. 4 is a schematic diagram of the giant ring-shaped combined nozzleformed by small nozzles with rectangular end sections.

FIG. 5 is a schematic diagram of the giant ring-shaped combined nozzleformed by small nozzles arranged along an elliptical ring.

FIG. 6 is a schematic diagram of the giant ring-shaped combined nozzleformed by small nozzles arranged along a rectangular ring.

FIG. 7 is a schematic diagram showing small primary air nozzles andsmall secondary air nozzles arranged on two concentric circular rings.

FIG. 8 is a schematic diagram showing the small primary air nozzles andthe small secondary air nozzles arranged on two circular rings that haveequal diameters and are not concentric.

FIG. 9 is a schematic diagram showing the small primary air nozzles andthe small secondary air nozzles arranged in a two-two concentrated mode.

FIG. 10 is a schematic diagram showing the small primary air nozzles andthe small secondary air nozzles arranged in a three-three concentratedmode.

FIG. 11 is a comparison diagram showing the velocity distributions in aboiler furnace with traditional burners and a boiler furnace withburners of the present disclosure.

FIG. 12 is a comparison diagram showing the temperature distributions inthe boiler furnace with the traditional burners and a boiler furnacewith the burners of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The specific embodiments of the present disclosure are further describedin detail below in combination with the accompanying drawings. Theseembodiments are only used to explain the present disclosure, not tolimit the present disclosure.

In the description of the present disclosure, the terminology usedherein for the purpose of describing particular examples is not intendedto be limiting for further examples. Whenever a singular form such as“a”, “an” and “the” is used and using only a single element is neitherexplicitly or implicitly defined as being mandatory, further examplesmay also use plural elements to implement the same functionality. Itshould be noted that orientation or position relationships indicated bythe terms “center”, “longitudinal”, “lateral”, “up”, “down”, “inner”,“outer” and so on are based on the orientation or position relationshipsshown in the drawings, which are only for the convenience of describingthe present disclosure and simplifying the description, rather thanindicating or implying that the device or element mentioned must have aspecific orientation, be constructed or operated in a specificorientation: therefore, it cannot be understood as a limitation of thepresent disclosure.

Furthermore, in the description of the present disclosure, unlessotherwise stated, “multiple” means two or more.

As shown in FIG. 1 , the present disclosure provides a wall-arrangedgiant ring-shaped straight-through pulverized coal burner. The burnerincludes burner nozzles arranged on four side furnace walls 100 of theboiler. The burner nozzles on the four side furnace walls 100 can form awall-tangential combustion mode in the furnace. Different from the priorart, each burner on each side furnace wall 100 is formed by multiplesmall nozzles arranged along a ring, giant ring-shaped combined nozzles10, 20, 30, 40 are formed on each furnace wall. These giant ring-shapedcombined nozzles 10, 20, 30 and 40 are arranged at different heights ofthe furnace wall 100. Four giant ring-shaped combined nozzles (such asthe four giant ring-shaped combined nozzles 10) on the four side furnacewalls 100 at the same height are installed with a certain distancedeviated from the centerlines of the furnace walls 100.Therefore,airflows ejected from the four giant ring-shaped combined nozzlesinteract with one another in the furnace to form a suitable combustiontangential circle, that is, a wall-tangential combustion mode.

A distance from the installation center of each giant ring-shapedcombined nozzle to its adjacent downstream furnace wall should begenerally greater than 0.7 times of the equivalent diameter of giantring-shaped combined nozzle, so that there is a certain distance fromthe small nozzles on the back-fire side of the giant ring-shapedcombined nozzle to the adjacent downstream furnace wall, to prevent theinjected airflows from adhering to the furnace wall caused by that theairflows on the back-fire side of the giant ring-shaped combined nozzleis too close to the adjacent wall surface.

As shown in FIGS. 2, 3 and 4 , the end section of each of the smallnozzles 1 and 2 forming the giant ring-shaped combined nozzle may besquare, circular or rectangular, or C-shaped as disclosed in the ChinesePatent CN104676585B.

As shown in FIG. 4 . 5 and 6, the small nozzles 1 and 2 forming thegiant ring-shaped combined nozzle may be arranged along a circular ring(as shown in FIG. 4 ), an elliptical ring (as shown in FIG. 5 ) or arectangular ring (as shown in FIG. 6 ).

As shown in FIG. 1 , the giant ring-shaped combined nozzles on thefurnace walls 100 include a plurality of giant ring-shaped combinednozzles 10, 20 and 30 in the main combustion region of the furnace, anda plurality of giant ring-shaped combined nozzles 40 in the burnout areaof the furnace. Each giant ring-shaped combined nozzle 40 in the burnoutarea of the furnace is formed by a plurality of small separated overfire air nozzles arranged in a ring-shaped mode. As shown in FIGS. 2-10, on the furnace walls corresponding to the main combustion region ofthe furnace, each giant ring-shaped combined nozzle is formed by aplurality of small primary air nozzles 1 and a plurality of smallsecondary air nozzles 2 arranged in a ring-shaped mode.

In a preferred embodiment, each giant ring-shaped combined nozzle 10, 20and 30 in the main combustion region includes 6 small primary airnozzles 1 and 6 small secondary air nozzles 2, and each giantring-shaped combined nozzle 40 in the burnout area includes 12 smallseparated over fire air nozzles. Small nozzles with square end sectionsare adopted, in which a side length of each small primary air nozzle 1is 0.36 meters, a side length of each small secondary air nozzle 2 is0.44 meters, a side length of each small over-fired air nozzle is 0.36meters, and an equivalent ring diameter of the giant ring-shapedcombined nozzle is 3.6 meters.

An area of the end section of the small primary air nozzle 1 may be lessthan, equal to or greater than that of the small secondary air nozzle 2.

As shown in FIGS. 2-6 , the small primary air nozzle 1 and the smallsecondary air nozzle 2 are arranged along the ring at intervals: morespecially, the small primary air nozzle 1 and the small secondary airnozzle 2 are alternately arranged on the same circular ring, the sameelliptical ring or the same rectangular ring to enhance the interactionsbetween the fuel stream and the combustion air to promote their mixing.

As shown in FIG. 7 , the small primary air nozzle 1 and the smallsecondary air nozzle 2 are arranged along two concentric circular ringsto form a giant ring-shaped combined nozzle. In some embodiments, thesmall primary air nozzle 1 and the small secondary air nozzle 2 may alsobe arranged along two concentric elliptical rings or two concentricrectangular rings to form a giant ring-shaped combined nozzle. FIG. 7shows that the small primary air nozzles 1 are arranged on the largeouter ring, and the small secondary air nozzles 2 are arranged on thesmall inner ring, which could be exactly opposite in other embodiments.

As shown in FIG. 8 , the small primary air nozzles 1 and the smallsecondary air nozzles 2 may also be arranged along two circular ringsthat have equal diameters and are not concentric, to form a giantring-shaped combined nozzle.

As shown in FIG. 9 , the small primary air small nozzles 1 and the smallsecondary air small nozzles 2 may also be arranged on a circular ring,an elliptical ring or a rectangular ring in a two-two concentrated mode;more specially, each two adjacent small primary air nozzles 1 and eachtwo adjacent small secondary air nozzles 2 are alternately arrangedalong a ring to form a giant ring-shaped combined nozzle.

As shown in FIG. 10 , the small primary air nozzles 1 and the smallsecondary air nozzles 2 may also be arranged along a circular ring, anelliptical ring or a rectangular ring in a three-three concentratedmode; more specially, three adjacent small primary air nozzles 1 andthree adjacent small secondary air nozzles 2 are alternately arrangedalong a ring to form a giant ring-shaped combined nozzle.

The total number of the small primary air nozzles and the smallsecondary air nozzles in each giant ring-shaped combined nozzle may benot less than 5, which may be increased with increasing boiler capacity.Power of each small primary air nozzle is not less than 3~5 MW. Adiameter or an equivalent diameter of each giant ring-shaped combinednozzle is not less than 1 meter, which increases with increasing boilercapacity. The above equivalent diameter refers to a diameter of a circlewhich has an area equal to the ring. For the giant ring-shaped combinednozzle with the small nozzles arranged along two rings, the equivalentdiameter refers to an average value of equivalent diameters of the tworings.

In some embodiments, in order to facilitate installation, the smallprimary and secondary air nozzles of the giant ring-shaped combinednozzle are installed perpendicular to the furnace wall surface, whichreduces the sensitivity to the installation angle compared with theexisting four-corner tangential boiler. Furthermore, the small nozzlescan be adjusted upward, downward, leftward and rightward; morespecially, an angle between the small primary air nozzle and the furnacewall surface and an angle between the small secondary air nozzle and thefurnace wall surface can be adjusted upward, downward, leftward andrightward according to the operation requirements, for controlling thesize of the actual tangential circle and the adjustment of the flamecenter position.

The inventor carried out computational fluid dynamics (CFD) numericalsimulation on the tangentially-fired pulverized coal boiler with thetraditional wall-arranged burners and the pulverized coal boiler withthe giant ring-shaped straight-through pulverized coal burners of thepresent disclosure to analyze the in-furnace flow and combustiondifferences under such two schemes. The calculation results are shown inFIGS. 11-12 , where FIG. 11 shows the velocity contour on cross sectionsat different heights in the furnace under two burner arrangements, andFIG. 12 shows the temperature field contour on the vertical middlesections in the furnace under the two burner arrangements.

From FIG. 11 , it can be seen that, compared with the boiler with thetraditional wall-arranged straight-through burners, a better tangentialcombustion circle is formed in the furnace of the boiler with theburners of the present disclosure, wherein the high-velocity zone nearthe furnace walls is reduced, and the phenomenon of flame scouring onfurnace walls is significantly alleviated. Therefore, the risk ofslagging and high-temperature corrosion on the heating surface of thefurnace caused by flame scouring on furnace walls is fundamentallyreduced, thereby improving the operation reliability of the boiler.

It can be seen from FIG. 12 that, the combustion temperature level inthe boiler with the burner of the present disclosure is increasedsignificantly, which indicates that adopting the scheme of burner of thepresent disclosure is also conducive to the processes of coal combustionand the subsequent heat release, thereby facilitating the improvement onthe boiler efficiency. In addition, it can be seen that, compared withthe boiler adopting the traditional wall-arranged tangential burners,the area of the low-temperature zone at the furnace center of the boilerusing the burner of the present disclosure is smaller, which shows thatthe traditional near-wall circular flame combustion mode can betransformed into a more uniform volume combustion mode in the presentdisclosure, which is conducive to improving the combustion uniformity inthe furnace.

In the present disclosure, the mutual entrainments of multiple airflowsin the giant ring-shaped combined nozzle make it difficult for eachindividual airflow to diffuse to the external space, thus helping toenhance the overall stiffness of the combined airflows. Furthermore, theswirling flue gas flow and the deflected upstream airflow in the furnacemainly impinge the fire-side airflows from the giant ring-shapedcombined nozzle, while the back-fire side airflows can maintain a strongstiffness since they are not directly impinged. The back-fire sideairflows with stronger stiffness play a role in supporting the firesideairflows that may be deflected, so it can effectively prevent the largedeflection of the fireside airflows.

The present disclosure provides a wall-arranged giant ring-shapedstraight-through pulverized coal burner, which is particularly suitablefor reconstruction of the existing boilers and design of new boilerswith large capacity of 200MW and above and with large size of furnace.The wall-arranged giant ring-shaped straight-through pulverized coalburner can significantly overcome the problems such as airflow scouringon furnace walls caused by the insufficient airflows stiffness, and thesubsequent slagging and high-temperature corrosion on the heatingsurface caused by the airflow scouring on furnace walls in largecapacity boilers, which can make the boiler operate more safely andstably. Furthermore, it is beneficial to control the formation ofnitrogen oxides during coal combustion process. In conclusion, thepresent disclosure can effectively overcome the defects in the prior artand improve the safety and stability of boiler operation, so it has highindustrial application value.

The above embodiments only illustrate the principle and effect of thepresent disclosure, not limit the present disclosure. Any personordinarily skilled in the art can modify or change the above embodimentswithout departing from the spirit and scope of the present disclosure.Therefore, all equivalent modifications or changes made by those withordinary knowledge in the technical field without departing from thespirit and technical ideas disclosed by the present disclosure shallstill be covered by the claims of the present disclosure.

What is claimed is:
 1. A wall-arranged giant ring-shapedstraight-through pulverized coal burner, comprising burner nozzlesarranged on four side furnace walls of a boiler, the burner nozzles onthe four side furnace walls form a wall-tangential combustion modeinside the boiler furnace, wherein each burner nozzle on each sidefurnace wall comprises a plurality of small nozzles arranged along aring to form a giant ring-shaped combined nozzle.
 2. The wall-arrangedgiant ring-shaped straight-through pulverized coal burner according toclaim 1, wherein the small nozzles forming the giant ring-shapedcombined nozzle are arranged along a ring selected from a groupconsisting of a circular ring, an elliptical ring and a rectangularring.
 3. The wall-arranged giant ring-shaped straight-through pulverizedcoal burner according to claim 1, wherein on each side furnace wallcorresponding to a main combustion region inside the furnace, aplurality of the giant ring-shaped combined nozzles are provided along afurnace height direction.
 4. The wall-arranged giant ring-shapedstraight-through pulverized coal burner according to claim 1, wherein oneach side furnace wall corresponding to the main combustion regioninside the furnace, the giant ring-shaped combined nozzle comprises aplurality of small primary air nozzles and a plurality of smallsecondary air nozzles arranged along the ring.
 5. The wall-arrangedgiant ring-shaped straight-through pulverized coal burner according toclaim 4, wherein the plurality of small primary air nozzles and theplurality of small secondary air nozzles are arranged at intervals withone another along the ring.
 6. The wall-arranged giant ring-shapedstraight-through pulverized coal burner according to claim 4, whereinthe plurality of small primary air nozzles and the plurality of smallsecondary air nozzles are arranged on a ring selected from a groupconsisting of a circular ring, an elliptical ring and a rectangular ringin a mode selected from a group consisting of a two-two concentratedmode and a three-three concentrated mode.
 7. The wall-arranged giantring-shaped straight-through pulverized coal burner according to claim4, wherein the plurality of small primary air nozzles and the pluralityof small secondary air nozzles are arranged on two rings selected fromthe group consisting of two concentric circular rings, two ellipticalrings and two rectangular rings.
 8. The wall-arranged giant ring-shapedstraight-through pulverized coal burner according to claim 4, whereinthe plurality of small primary air nozzles and the plurality of smallsecondary air nozzles are respectively arranged on two circular ringswhich have equal diameters and are not concentric.
 9. The wall-arrangedgiant ring-shaped straight-through pulverized coal burner according toclaim 1, wherein on each side furnace wall corresponding to a burnoutarea at an upper part of the furnace, the giant ring-shaped combinednozzle comprises a plurality of small separated over fire air nozzlesarranged in a ring.
 10. The wall-arranged giant ring-shapedstraight-through pulverized coal burner according to claim 1, whereinthe small nozzles installed on the side furnace wall are adjustedupward, downward, leftward and rightward.